Prosthetic limbs are used by thousands of patients who have had a portion of a limb amputated due to disease or injury. Generally, the prosthetic limb includes a socket and a weight-bearing portion. The patient inserts part of their remaining limb, the residual limb, into the socket to secure the prosthetic limb to the body.
The socket is generally sized to form a tight fit around the surface of the residual limb, with the goal of providing secure contact with the entire residual limb surface. By maintaining contact with as large a surface area as possible, the patient's weight is distributed over a larger surface area within the socket. This helps to ensure that the prosthetic limb maintains a secure attachment to the residual limb, allowing efficient transfer of intended movement of the residuum to the device (prosthesis).
Most patients experience some changes in the volume of the residual limb throughout the day. These changes may be caused by a variety of factors including, for example, perspiration, temperature changes, or physiologic changes due to medical problems or medications. Regardless of the cause, limb volume changes may cause the socket to fit improperly, making the prosthetic uncomfortable or causing the device to loosen or fall off. Therefore, management of limb and socket volumes is important for maintaining an appropriate fit.
One method for securing a prosthetic to a residual limb is disclosed in U.S. Pat. No. 6,726,726, which issued to Caspers on Apr. 27, 2004 (hereinafter the '726 patent). The method of the '726 patent includes creating a vacuum within the socket using a pump attached to the prosthetic limb. Although this method may provide suitable attachment of a prosthetic, it has several drawbacks. For example, to create the vacuum, the method of the '726 patent requires a mechanical pump to be attached to the prosthetic. The pump adds considerable weight to the prosthetic, making it unwieldy and/or uncomfortable for some patients. In addition, suitable pumps may be very expensive.
It is accordingly an object of the present invention to provide improved prosthetics that can produce a negative pressure within the device socket without the use of an active pump.